Emulsions - Instability mechanisms
4 important questions on Emulsions - Instability mechanisms
Emulsion stability is a combination of 2 things
- Emulsion formation --> smaller proteins diffuse quicker to interface than larger proteins
- Interfacial thickness --> thicker interface prevents coalescence. Larger proteins wanted
Which main process cause the instability of emulsions?
- Flocculation --> at high concentrations, droplet may form a network and a gel
- Coalescence --> during homogenisation, but not during storage
- Creaming or sedimentation --> oil and air are lighter, so they cream
- Ostwald ripening (for emulsions) and disproportionation (for foams) --> polydisperse size-distribution needed, fluid inside droplet is slightly soluble in continuous phase
Does Ostwald ripening occur as much in emulsions as disproportionation in foams?
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Which 3 forces act in sedimentation/creaming?
- Gravitational force
- Buoyancy force --> opposite to the direction of the gravitational force
- Friction force --> friction that acts on the moving particle, direction opposite of the direction to which the particle moves
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